It has been the case that wrinkles formed on the face (such as the outer corners of the eyes and the cheeks) of a subject are caused with a twist due to a change in the facial expression (for example, laugh lines or anger lines) or pressing on the skin. Furthermore, for reasons such as aging or the decline of skin texture or elasticity, wrinkles no longer disappear even when the expression returns (so-called residual wrinkles), so as to ultimately become wrinkles that are caused irrespective of expressions (so-called fixed wrinkles). Accordingly, wrinkles have become a major cosmetic issue as a symbol of the aging phenomena of appearance, so that consumers have expected much from the development of products that are effective in preventing or reducing wrinkles. Furthermore, in the development of anti-wrinkle products, it is important to demonstrate their performance and effects by a scientific and highly-reliable evaluation method.
Therefore, the standardization of a wide variety of wrinkle assessment methods has been performed by creating guidelines for evaluating the functions of anti-wrinkle products for wrinkles at the outer corners of eyes (for example, see Non-Patent Document 1.) Furthermore, there has been the technique of calculating the depth and area of each wrinkle from the three-dimensional shape data of the outer corner of an eye and assessing wrinkles based on a distribution analysis to which the results of a visual assessment are added (for example, see Non-Patent Document 2).